DIFFERENT differentials - do you beg to differ?

[SHY]

Back in the 80s we had the gear diffs. Those were quite smooth I thought back then, and practically maintenance free.

Then the ball diffs came (I now know that Cecil Schumacher invented it, and that their logo illustrates just that, thx)... They cost more than the whole car and were much better it was claimed.

Can someone do a short story about why this is better?

I'm quite sure I read that Serpent is making a gear diff for their S400 (TC), that would be adjustable? Anyone got more on this? Will they try it also in the S500?

Personally I think the ball diffs work fine, but they don't last very long. For 1:12 it sucks big time! One single run and it's not smooth anymore... Not far as troublesome in 1:10 OR, but still I find it too much work (I'm lazy by nature).

1:8 OR cars use gear diffs because of the abuse right?

Give your thoughts and ideas! Can the ball diff be improved? Can gear diffs be just as good? New and even better solutions?

1:8 TR has a solid rear axle and a front one-way... now that's easy for ya!

SMP tried with a one-way in the rear axle many years ago... why? To stop the WHOLE transmission when coasting... Has this been tried in 1:10 OR?

[Chrislong]

Originally Posted by SHY

SMP tried with a one-way in the rear axle many years ago... why? To stop the WHOLE transmission when coasting... Has this been tried in 1:10 OR?

How would 1/10th OR perform with two one ways, and brakes via servo and disk?

Id like to cut out the maintenance of ball diffs, when they are good they feel great but when they go they're a pain at times. Plus the quality of the chinese AE and Losi stuff is far lower than what the Losi and AE stuff were like back in the early days of the B4 and Losi xxx/xx4.

Chris

[Lee]

How would you slow the car down with one ways at either end?

[SHY]

Originally Posted by Lee

How would you slow the car down with one ways at either end?

The Slide had a brake disk directly on the rear axle

They gave it up for 1:8 TR though, too much power so they never got it to be reliable...

@Chris: I'd love to try an RC car with a dedicated servo for the brakes! (not legal) You'd operate this with your foot, so you could brake and give throttle at the same time, to keep the momentum through the corner - just like when racing 1:1 scale

[Chrislong]

Originally Posted by Lee

How would you slow the car down with one ways at either end?

LOL, Disk brakes via a servo dude

SHY guy, that'd be cool - proper toe and heal racing with a buggy.

[josh_smaxx]

Serpent HAVE made a geared diff for the S400, most of the team drivers are using it and think its great. Its adjustable by changing the thickness of oil in it (same as 1/8th OR diffs). Its only 5g heavier than the ball diff (are there light!) and the people using it much prefer it due to the reduced maintence and much more reliable tuning (its the same everytime you use it whereas with building a ball diff every 3 or 4 races its difficult to get it exactly the same every rebuild).

[Chrislong]

Originally Posted by josh_smaxx

(its the same everytime you use it whereas with building a ball diff every 3 or 4 races its difficult to get it exactly the same every rebuild).

If I have 5 new ball diffs to build, all 5 will be identical once built. its easy.

Your comment is only valid if talking about rebuilding a ball diff with used parts. What tends to happen then is it'll be smooth until the grease is run in, then it'll just be dog rough again.

[Lee]

Originally Posted by Chrislong

LOL, Disk brakes via a servo dude

SHY guy, that'd be cool - proper toe and heal racing with a buggy.

I understand it would need a disc brake but you would have to have them in the drive shafts if you wanted each wheel to be independent


Also, i have never rebuilt diffs every few races, i raced open diff cars for years and i only ever rebuilt them after a wet race, a lot of it is down to the grease you use

[josh_smaxx]

Originally Posted by Lee

Also, i have never rebuilt diffs every few races, i raced open diff cars for years and i only ever rebuilt them after a wet race, a lot of it is down to the grease you use

I used the Serpent stuff that came with it, then i moved onto the schumacher stuff and its ALOT better, would highly recommend it.

I have raced it twice now on one build, its getting raced again then rebuilt, i like to keep on top f the maintenance, would hate to loose and think its because the diff wasnt up to scrath ect.

[sparrow.2]

Originally Posted by Lee

I understand it would need a disc brake but you would have to have them in the drive shafts if you wanted each wheel to be independent

You could make it work with center one-ways and brake discs on the gearbox input shafts.

You would be adding a lot of weight though for a very questionable advantage.

You can achieve a si,ilar effect by turning off autobrake altogether on brushless setups. I tried this and basically found that the car tends to understeer more than if you have autobrake dialled higher since it doesn't transfer as much weight to the front when you let off the power.

Hope that made sense...

[SHY]

Originally Posted by Lee

I understand it would need a disc brake but you would have to have them in the drive shafts if you wanted each wheel to be independent


Also, i have never rebuilt diffs every few races, i raced open diff cars for years and i only ever rebuilt them after a wet race, a lot of it is down to the grease you use

The actual car that had this had a ventilated brake disk as part of the outdrive:

The oneway sat inside the rear pulley. So this worked just fine, except for the 1:8 power being too brutal for the one-way. Keep in mind that the driving force applied to the front wheels are a joke compared to what's going on in the rear!

Anyways, for electric we would need a small brake servo in addition to the ESC to be able to brake and give throttle simultaneously... not legal but I've always wanted to try this! Electric motors respond quickly, but for a gas engine you could keep the clutch engaged and the revs up... and for all classes you'd keep the car more stable going through fast sections!

I've been doing RC all my life, and I've learned to hate a few things:
-radio interference
-cleaning bearings
-maintaining brushed motors
-rebuilding diffs

I find it very difficult to build two identical diffs. Not to mention that they should be broken in after each rebuild (incl. sanding down the plates and so on), and gradually tightened. Takes a lot of time! I'd LOVE to just be able to tune a gear diff, and note down my setup... Btw I seem to recall that Serpent had on its Impact some years ago a special diff. I think the diff itself was always the same. And there was an adjustment of some friction plastes in addition... think it worked very well! (don't recall if that was a ball or gear diff though)

Is it really as good as a ball diff??? Why did we then get ball diffs in the first place???

And more: if we go back to gear diffs... we can then have torsen diffs, tactyl diffs... or would that not be as suitable as for 1:8 OR? Keep in mind that with LiPos next year we can add some weight back on the cars...

Originally Posted by sparrow.2

You could make it work with center one-ways and brake discs on the gearbox input shafts.

You would be adding a lot of weight though for a very questionable advantage.

You can achieve a si,ilar effect by turning off autobrake altogether on brushless setups. I tried this and basically found that the car tends to understeer more than if you have autobrake dialled higher since it doesn't transfer as much weight to the front when you let off the power.

Hope that made sense...

I just make these presumtions, I'm not quite sure:
-the tranny should be as free moving as possible. When coasting I'd wish it was "gone". And no motor brake / drag whatsoever
-the only thing slowing the car down (except when braking) should be the friction between the wheels and the ground

I feel this caters for smoother, more consistent & faster cornering. And in many cases it's faster not to use brakes at all...